The present disclosure relates to a drive unit including a vibratory actuator and a relatively-movable member.
Conventionally, a drive unit including a vibratory actuator and a relatively-movable member has been known. Specifically, the vibratory actuator includes an actuator body including piezoelectric elements; and driver elements attached to the actuator body. The vibrator actuator is arranged so that the driver elements contact the relatively-movable member. In the drive unit, vibration is generated in the actuator body to generate elliptical motion of the driver elements in response to such vibration, thereby relatively moving the relatively-movable member or the vibratory actuator.
In this manner, the vibratory actuator outputs drive force through friction force between the driver elements and the relatively-movable member, and therefore there is a problem of abrasion on a surface of the relatively-movable member, which contacts the driver elements. On the other hand, if the contact surface is mirror-finished to reduce the abrasion on the contact surface, chattering noise is generated between the driver elements and the contact surface, and such a state is not preferred in practical use.
In a drive unit disclosed in Japanese Patent Publication No. 09-331687, streaks are formed by polishing in a surface of a relatively-movable member, which contacts driver elements, so that an average center line roughness (Ra) of the contact surface is equal to or greater than 0.05 μm, and equal to or less than 1.0 μm. This reduces abrasion on the contact surface while reducing generation of chattering noise on the contact surface.